New technology developments allow the creation of more and more immersive multimedia systems. 3D images and sound spatialization are now present in the end-user living space. In line with those new enhancements, alternative technologies propose to extend the audiovisual experience by providing ambient lighting. For ambient lighting several light spots composed of three colored LEDs are located around the screen. These light spots provide light effects in accordance with the content of the video that is displayed on the screen.
To be efficient and immersive, such systems have to provide a lighting color that is appropriate for the visual content. The different technologies available on the market generally adopt a similar strategy that will be detailed hereafter.
The screen is divided into several areas depending on the position and the number of lighting units. The areas may be spread all over the screen or only along the borders, close to their associated lighting unit. One area is generally associated to one lighting unit. The color to render by each unit is determined by the color properties of the corresponding area. Two different methods are generally considered. The first one consists in choosing the average color in each of the separated areas, whereas the other one uses the main hue and saturation in each of these areas of the screen.
A more advanced method for determining colors to be emulated by an ambient light source is disclosed, for example, in US 2007/0242162. The colors are extracted from video content using perceptual rules for intelligent dominant color selection. The scene content is taken into account when determining the colors. For this purpose content analysis is used.
Even though the available systems provide interesting effects, the underlying technologies are often not accurate enough to nicely extend the screen, especially when the number of light devices is reduced. Indeed, the mean color or the main hue and saturation components do not necessarily match the actual “ambient” color and it can lead to unexpected renderings.